Method of making stencils



1, 1955 R. w. HENNINGSGARD 9 METHOD OF MAKING STENCILS Filed July 27, 1953 Big-1 13; wen/liar Russell U7. Msnninyayawcl United States Patent METHOD OF MAKING STENCILS Russell W. Henningsgard, Minneapolis, Minn.

Application July 27, 1953, Serial No. 370,385

3 Claims. (Cl. fill-128.2)

This invention relates to improvements in the art of making stencils for printing by the so-called silk screen process. In such process, a negative of the copy, comprising the design of lettering and/or ornamentation to be reproduced, is made by causing a film to adhere to certain areas of a screen of silk or other suitable foraminous material of fine mesh. This film-treated screen is used in printing by squeegeeing ink, paint or other printing material through the interstices of the screen which remain unobstructed by the film, thus causing the printing material to be deposited on the surface of a sheet, card or other surface upon which the screen is superimposed during the operation.

In applying film material [.0 various areas of a screen, I employ what is called a stencil sheet, the same being of the nature patented by Louis F. DAutremont in United States Letters Patent No. 1,781,834 of November 18, 1930. Such a stencil sheet comprises a backing sheet of wax paper or the like having thereon a film coating of shellac or other suitable material faced with an adhesive substance such as lacquer or glue. This facing, when dry, provides the film coating with a hard smooth outer surface which may be softened to render it adhesive, as by moistening the same with a suitable liquid. A stencil sheet of the nature disclosed by DAutremont is neces sarily at least semi-transparent and, according to his teachings in the use of such stencil sheet, it is superimposed over previously prepared copy with the film coating of the stencil sheet uppermost. Guided by the copy to be reproduced, which is seen through the stencil sheet, those portions of the film coating of said stencil sheet lying above and corresponding to said copy are severed from the body of the film by means of a knife or stylus and peeled from the backing sheet which remains intact. A screen is placed against the stencil sheet in contact with the film coating remaining thereon. A solvent is applied through the screen to the adhesive surface of the film coating to soften the same and, while said surface is soft, the screen is pressed against it causing the film coating of the stencil sheet to adhere to the screen. Thereupon, the backing sheet is peeled away from the film coating adhering to the screen, thereby completing the silk screen negative for reproduction of the copy previously followed in cutting and peeling away portions of the film coating of the stencil sheet.

In the present improved method of forming a printing stencil, I employ no separate initially prepared copy to be viewed through the stencil sheet in guiding the cutting out of corresponding portions of the stencil sheet film coating from the body of such coating. In fact, in my method, there is no cutting out at all of portions of stencil sheet film coating from the body thereof.

The copy or design to be reproduced in the ultimate printing stencil, made in accordance with my invention, is painted or otherwise suitably applied directly to the face of the film coating on the backing sheet of a stencil sheet, thereby masking certain areas of the film coating in correspondence with the copy to be reproduced. The screen is then superimposed upon the stencil sheet in contact with the masked face of its film coating. Thereupon, through the screen, a film-softening solvent is applied to the film coating which, except for the masked areas thereof, becomes adhesively afiixed to the screen under pressure bringing the screen and stencil sheet firmly together. Finally, the backing sheet of the stencil sheet is peeled away from those portions of the film coating adhering to the screen taking with said backing sheet the 2,700,930 Patented Feb. 1, 1955 masked portions of said film coating, which, by reason of imperviousness of the masking coating to the solvent used, do not adhere to the screen, but remain in adherence with said backing sheet. Thus, the areas of the film coating of the backing sheet, outlined by the mas ing coating thereon, are severed by tearing from the remaining areas of the body of the film coating adhering to the screen and are removed from the screen with the backing sheet when it is peeled from said screen.

This severance by tearing of the masked areas of stencil sheet film coating from the remaining areas there of when the backing sheet is peeled away from the screen, is in contrast to DAutremonts severance of areas of film coating by cutting, as with a knife or stylus, before the stencil sheet is applied to the screen.

An object of my invention, therefore, is to provide an improved method for making printing stencils, which involves the use of conventional types of screens and stencil sheets and yet effects a substantial saving in time, labor and costs of production of such stencils, a more specific object of my invention being the elimination of the laborious and painstaking task of cutting out by knife or stylus certain areas of a stencil sheet film coating along lines corresponding with the outlines of previously prepared copy seen through the stencil sheet.

To the accomplishment of the foregoing and other objects, the invention, then, consists of the method hereinafter fully described and particularly pointed out in the claims.

Accompanying the following detailed description of my improved method of making printing stencils is a drawing, in which: I

Fig. l is an elevational view of a stencil sheet, as seen from the film-coated side thereof, the film coating being shown with masking material thereon masking certain areas thereof in correspondence with the copy to be reproduced by a printing stencil to be made.

Fig. 2 is an enlarged deta1l sectional view, taken as on the line 22 of Fig. 1.

Fig. 3 is an elevational view showing a screen fragmentarily and illustrating also the stencil sheet shown in Fig. 1, that portion of the backing sheet of said stencil sheet, bearing thereon the masked areas of the film coating of said stencil sheet, being portrayed as peeled away from the screen, the remaining areas of said film coating being shown as adhering to the screen.

Fig. 4 is an enlarged detail sectional view, taken as on the line 4-4 of Fig. 3.

Fig. 5 is a detail sectional view, also on an enlarged scale, taken as on the line 55 of Fig. 3.

The printing stencil provided in carrying out the method, constituting the present invention, comprises the familiar fine-mesh screen of silk or other suitable material such as that indicated at 10 in Figs. 3 and 4. As in conventional practice, the screen 10 is preferably held taut in a suitable frame (not shown) and, after it has had a film applied to certain areas thereof leaving other of its areas clear in correspondence with the copy to be reproduced by the stencil, the film-treated screen is superimposed upon the surface to be printed, and ink, paint or other printing material is forced, as by means of a squeegee, through the clear areas of said screen onto said surface, the said film-treated screen. being thereafter removed from the printed surface.

To provide for the application of a film to certain areas of a screen, I employ a stencil sheet, as at A, the same being of the nature of the stencil sheet disclosed in the aforementioned Patent No. 1,781,834 to DAutremont. Such a stencil sheet consists of a backing sheet 11 having a film coating 12 thereon which may be peeled therefrom. As customary, the outer surface of said film coating 12 is normally hard and smooth but may be softened and rendered adhesive by moistening it with a solvent to which it is responsive.

Conventionally, a stencil sheet of the nature aforesaid is at least semi-transparent so that copy to be reproduced laid out on a sheet or other surface can be seen clearly enough through the stencil sheet to enable a person with knife or the like to cut through the film coating to'the backing sheet of the stencil sheet, following the outlines of the layout, preparatory to the customary peeling from the backing sheet of the severed areas of the film coating. Transparency of the stencil sheet is not a requisite in the practice of my improved method, which eliminates the necessity of making a separate layout and following the outline thereof, by sight through the stencil sheet, with a cutting instrument to sever from the body of the film coating those areas thereof which correspond with the layout. My method provides for the making of a layout directly upon the face of the film coating of the stencil sheet with material which masks those areas of the film coating corresponding to the copy to be reproduced by the ultimate stencil. Said masking material in whatever form employed will be unresponsive to the solvent to which the unmasked portion of the film coating responds in the softening of the same for adhesion to a screen. While paint to be applied with a brush, or by spray or otherwise through a suitable stencil, is preferred as a masking material, such material may be in the nature of an ink to be applied by pen, or by printing with a stamp or other medium, or said masking material may be sheet material adapted to be adhesively applied to the film coating of the stencil sheet.

In the drawing, the masking material, applied to the film coating 12 of the stencil sheet A and constituting the layout of the letters R and H to be reproduced, is designated by the reference numeral 13.

Having applied the masking material, as at 13 in Fig. 1, to the film coating 12 of the stencil sheet A, the screen (Fig. 3) is superimposed upon the stencil sheet against the face of the film coating 12 bearing said masking material. Thereupon, a solvent is applied to said face of the film coating through the screen 10. The masking material 13 used in making the layout on the film coating 12 will be unresponsive to the solvent used. Conversely, said film coating will be responsive to the solvent and will become softened at the faces of those areas thereof not covered by the masking material 13. With the solvent-treated film coating 12 softened at its unmasked areas, it is caused to adhere, at those areas, to the screen 10 by pressing said screen against the film coating. The masking material 13 on the film coating 12 being unresponsive to the solvent, said coating beneath said material remains unaffected by the solvent and free from adherence to the screen.

After the solvent-treated screen 10 and stencil sheet 12 has become dry, the film coating 12, except at its masked areas, adheres to the screen 10 with greater tenacity than it does to the backing sheet of said stencil sheet. Said condition prevailing, the backing sheet 11 is stripped or peeled away from those areas of the film coating 12 adhering to the screen 10, this operation being illustrated in Fig. 3. In said operation, the masked areas of the film coating 12 and the masking material 13 thereon remain intact on the backing sheet 11 (Fig. 5), said masked areas of said film coating 12 being torn from the body of such coating adhering to the screen 12 when the backing sheet 11 is parted therefrom.

It will be understood that the film coating of a stencil sheet employed in carrying out the present method of making stencils will be susceptible of being severed by tearing so that the severing of the masked areas of film coating adhering to the backing sheet from those areas of said coating adhering to the screen may be accomplished along relatively sharp lines, thereby sharply to outline the copy to be reproduced by the stencil.

Having described the invention, what is claimed as new and desired to be protected by Letters Patent is:

1. The method of forming a printing stencil comprising a screen and a film adhering to certain areas thereof, said method employing a screen, a backing. sheet having a film coating thereon separable therefrom, masking material, and a solvent to which the film coating on the backing sheet is responsive and to which the masking material is unresponsive, said method consisting incovering with the masking material certain areas of the film coating on the backing sheet corresponding to the copy to be reproduced from the ultimate printing stencil, performing, one after the other, the next of two steps, namely, placing the screen against the film coating on the backing sheet, and applying the solvent to said film coating, thereby causing the unmasked areas of said film coating to adhere to the screen, and then peeling the backing sheet from the unmasked areas of film coating adhering to the screen and, simultaneously therewith, severing the masked areas of the film coating from said unmasked areas thereof and clearing the screen of said masked areas of said film coating unseparated from and along with said backing sheet.

2. The method of forming a printing stencil comprising a screen and a film adhering to certain areas thereof, said method employing a screen, a backing sheet having a film coating thereon separable therefrom, masking solution adapted to set as a coating, and a solvent to which the film coating on the backing sheet is responsive and to which a coating of the masking solution, when set, is unresponsive, said method consisting in coating with the masking solution certain areas of the film coating on the backing sheet corresponding to the copy to be reproduced from the ultimate printing stencil and permitting said masking solution to set, performing, one after the other, the next of two steps, namely, placing the screen against the masked film coating of the backing sheet, and applying the solvent to said film coating, thereby causing the unmasked areas of the film coating to adhere to the screen, and then peeling the backing sheet from the unmasked areas of film coating adhering to the screen and, simultaneously therewith, severing the masked areas of the film coating from said unmasked areas thereof and clearing the screen of said masked areas of said film coating unseparated from and along with said backing sheet.

3. The method of forming a printing stencil comprising a screen and a film adhering to certain areas thereof, said method employing a screen, a backing sheet having a film coating thereon separable therefrom, masking paint, and a solvent to which the film coating on the backing sheet is responsive and to which the masking paint, when dry, is unresponsive, said method consisting in applying the masking paint directly to certain areas of the film coating on the backing sheet corresponding to Y the copy to be reproduced from the ultimate printing stencil and permitting said masking paint to dry, superimposing the screen upon the paint-masked film coating of the backing sheet, applying the solvent to the film coating through the screen and pressing said screen against the solvent-treated film coating, thereby causing the unpainted areas of the film coating to adhere to the screen, and then peeling the backing sheet from the unpainted areas of film coating adhering to the screen and, simultaneously therewith, severing the paint-masked areas of the film coating from said unpainted areas thereof and clearing the screen of said paint-masked areas of said film coating unseparated from and along with said backing sheet.

No references cited. 

